Size matters: influence of dwarfing genes and the Lcol-A1 allele on coleoptile growth and crop establishment in wheat (Triticum aestivum)

Context Deep sowing allows growers to access deep soil moisture and ensure timely crop establishment in maximising yield potential. However, wheat cultivars containing the ‘Green Revolution’ Rht1 and Rht2 dwarfing genes often exhibit reduced crop establishment when sown deeper than 60 mm because of short coleoptile length (CL). Novel gibberellin biosynthetic mutant dwarfing genes associated with reduced plant height and greater CL offer potential alternatives to Rht1 and Rht2. Aims Determine CL and coleoptile diameter (CD) for genotypes and near-isogenic lines (NILs) with alternative dwarfing genes and a novel CL allele, and to validate plant establishment when sown deep in fields. Methods A diverse set of 101 wheat genotypes containing different dwarfing genes, including a novel long coleoptile allele, Lcol-A1, were assessed for CL and CD in temperature-controlled growth-chamber experiments (CE). The CE-phenotyped CL and CD were validated for plant establishment with shallow (4–5 cm) and deep (11–15 cm) sowing in two field experiments. Key results Compared with genotypes with Rht1 and Rht2, CL was significantly longer in genotypes with Rht13 (+23%), Rht18 (+24%), and Lcol-A1 (+16%) alleles across CE experiments. Longer CL significantly improved crop establishment with deep sowing in the field (16 and 33 plants m−2 for short- and long-coleoptiles respectively). Conclusion Longer CL associated with Rht13, Rht18 and Lcol-A1 allele improved crop establishment. Lcol-A1 allele was linked to a small increase in grain yield with deep sowing, while Rht18 was comparable to Rht2 with deep sowing. Implications Gibberellin-biosynthetic dwarfing genes, together with the Lcol-A1 allele, show promise for improving establishment with deep sowing.